Crankcase breather



Jan. 18, 1966 J. CADIOU CRANKGASE BREATHER 2 Sheets-Sheet 1 Filed March 31, 1964 Jan. 18, 1966 J. CADIOU CRANKGASE BREATHER 2 Sheets-Sheet 2 Filed March 51, 1964 United States Patent Ofilice 3,229,591 Patented Jan. 18, 1966 3,229,591 CRANKCASE BREATHER Jean Cadion, Paris, France, assignor to Societe Anonyrne Andre Citroen, Paris, France Filed Mar. 31, 1964, Ser. No. 356,270 Claims priority, application France, Apr. 3, 1963, 930,275, Patent 1,367,470 3 Claims. (Cl. 92-82) In certain piston engines and machines such as compressors, internal combustion engines, etc. the inner volume of the crankcase varies between two end values according as the pistons are more or less remote from their top dead center position or their bottom dead center position; this applies notably to flat-twin engines.

This variation in the crankcase volume produces a variation in the inner pressure which is a cause of leakages and various disturbances.

The conventional solution consists in creating a negative pressure or vacuum in the crankcase.

It is the essential object of this invention to provide a crankcase breather adapted to create a vacuum in the crankcase up to velocities of rotation of, say 6,000 revolutions per minute without causing any oil to be expelled from the engine.

To this end, the crankcase is connected with the interposition of a valve to a first chamber comprising at its lower portion a return duct leading to the crankcase, said first chamber being connected in turn with the interposition of another valve to another chamber communicating with the atmosphere.

Of course, any suitable type of valve may be used in this device.

In order to afford a clearer understanding of this invention and of the manner in which the same may be carried out in practice, reference will now be made to the accompanying drawing illustrating diagrammatically by way of example two forms of embodiment of the invention. Inthe drawings:

FIGURES 1 and 2 show a two-stroke flat-twin engine equipped with a crankcase breather according to a first form of embodiment of this invention, the pistons being respectively in bottom dead center and top dead center positions;

FIGURES 3 and 4 are explanatory diagrams showing crankcase pressure variance;

FIGURE 5 illustrates a valve suitable for carrying out this invention;

FIGURE 6 is a longitudinal section showing a modified form of embodiment of the crankcase breather of this invention;

FIGURE 7 is a fragmentary view similar to FIGURE 6 but showing details on a larger scale;

FIGURE 8 is a cross section taken upon the line VIII-- VIII of FIGURE 7.

The two-cylinder flat-twin engine illustrated in the drawings comprises a crankshaft 1 having its connectingrods 2, 3 attached to the pistons 4, 5 reciprocated in horizontal cylinders 6, 7.

The crankcase 8 in which the crankshaft 1 and connecting-rods 2, 3 are mounted constitutes a capacity bounded laterally by the pistons 4, 5 and during the engine operation its volume is altered to a considerable extent from a minimum value to a maximum value as shown in FIGURES 1 and 2 in which the pistons are in their bottom dead center and top dead center positions, respectively.

The upper portion of crankcase 8 is connected through a pipe line or like duct means 9 to a compartment 10 communicating through a valve 11 with the first cham her 12 the lower portion of which is connected through a return pipe line or duct 15 to the crankcase.

This first chamber 12 is connected in turn through another valve 16 to another chamber 17 communicating through the nozzle 18 to the atmosphere.

In the absence of the breather of this invention consisting of these three chambers 10, 12 and 17 with their companion pipe lines 9 and 15, the pressure within the crankcase 8 would vary according to a sinusoidal curve as shown in FIGURE 3, this curve comprising above and beneath the mean pressure line alternating high-pressure and low-pressure zones.

Due to the provision of the adjusted valves 11 and 16 allowing air to escape when the pressure exceeds a predetermined value the overpressure values are limited and the pressure curve is modified as shown in FIGURE 4; thus, the mean pressure value is reduced considerably and therefore the desired negative pressure or vacuum is produced in the crankcase.

Moreover, the small amounts of oil likely to be carried along by the escaping air into the chamber 10 and through valve 11 are collected in chamber 12 and return by gravity into the crankcase through the pipe line 15, this return being also caused by the fact that the mean pressure prevailing in chamber 12 exceeds that prevailing in chamber 10.

The valve 16 which may have the same adjustment as valve 11 permits the escape of air into chamber 17 and the venting of this air to the atmosphere through the pipe 18, while preventing any oil carried along into chamber 12 to escape therefrom.

Other types of valves may be used, notably the aerodynamic valve illustrated in FIGURE 5 and constituting the subject-matter of a French patent application filed by the same applicant on April 2, 1963, and entitled Aerodynamic Valve for High-Frequency Operation; this valve consists of a tube 19 in which a plurality of frustoconical elements 20, 21, 22 and 23 are disposed in series and inclined alternately in opposite directions.

The crankcase breather according to the modified form of embodiment shown in FIGURES 6 to 8 of the drawings comprises a central tube 24 connected at its lower end to the crankcase and closed at its upper end by a plug or cap 25. This tube 24 has a number of spaced radial holes 26 formed through its central portion at the level of a sleeve 27 of rubber or other suitable elastomer formed in turn with longitudinal slits 28 acting as a first valve means. This resilient sleeve is formed with a recessed or chambered inner intermediate portion 39 extending equally above and under the holes 26 so that these holes are not closed by said sleeve in the inoperative condition; this sleeve is properly positioned along the central tube 24 by means of diametrally opposite inner studs 40 engaging corresponding holes or recesses 41 formed in the central tube 24. Another valve 29 consists of a washer or disc 29 of rubber or other suitable elastomer, this washer or disc being secured along its peripheral edge by suitable means 30 on a support 31 and closing the upper portion of a chamber 32 bounded internally by a socket 33 and externally by a tube 34 connected at its lower portion to the tube 24 by means of a frustoconical portion 35; the circular inner edge of washer 29 fits tightly on the tube 24 and permits the outflow of air when the air pressure exceeds a predetermined limit value so as to lift this inner edge, the air thus released entering the chamber 36 and being vented to the atmosphere through a duct 37; at the lower frustoconical portion 35 of chamber 32, a side duct or branch pipe 38 connects this chamber to the crankcase (not shown).

The operation of this alternate form of embodiment of the crankcase breather of this invention is the same as that of the preceding form of embodiment described with reference to FIGURES 1 and 2 of the drawings; in this case, the valve means 27, 28 are substituted for the valve 11 and valve 29 is substituted for valve 16, the first chamber consisting of tube 24 having the same function as chamber 10 in the preceding form of embodiment, the second chamber being chamber 32 having the same function as chamber 12 of the first form of embodiment, and chamber 36 being finally substituted for chamber 17.

Of course, anybody conversant with the art will readily understand that, as clearly proved by the constructional differences and the same functional characteristics and principles of the two forms of embodiment shown and described herein, many modifications may be brought to these forms of embodiment without departing from the spirit and scope of the invention, as set forth in the appended claims.

What I claim is:

1. A crankcase breather adapted to create a vacuum in a crankcase containing a crankshaft and connecting-rod assembly, which comprises a first chamber connected to said crankcase, a valve disposed between said crankcase and said first chamber, a return duct from said first chamber to said crankcase which leads from the lower portion of said first chamber, another chamber overlying said first chamber, valve means between said first chamber and said other chamber, and duct means between said other chamber and the atmosphere.

2. A crankcase breather according to claim 1, consisting of a central tube of which the lower portion communicates with said crankcase and the upper portion is closed, said central tube having spaced radial holes formed at a common level therethrough, a valve-forming sleeve of elastic material fitting around said central tube at the level of said holes, said valve-forming sleeve having longitudinal slits formed therein which extend along one portion of its height, a first chamber surrounding said tube and said sleeve, a return duct leading from the lower portion of said first chamber to said crankcase, another chamber overlying said first chamber and also surrounding said central tube, other valve means between said chambers, and means permitting the communication between said other chamber and the atmosphere.

3. A crankcase breather as set forth in claim 2, wherein said elastic sleeve is formed with an inner recessed portion such that in the inoperative condition it will not close said holes.

References Cited by the Examiner UNITED STATES PATENTS 1,184,344 5/1916 Harley 92261 X 1,746,215 2/1930 Dearborn 12341.86 2,245,207 6/ 1941 Lundquist 92261 2,493,617 1/1950 Chubbuck 1234l.86 X

SAMUEL LEVINE, Primary Examiner. 

1. A CRANKCASE BREATHER ADAPTED TO CREATE A VACUUM IN A CRANKCASE CONTAINING A CRANKSHAFT AND CONNECTING-ROD ASSEMBLY, WHICH COMPRISES A FIRST CHAMBER CONNECTED TO SAID CRANKCASE, A VALVE DISPOSED BETWEEN SAID CRANKCASE AND SAID FIRST CHAMBER, A RETURN DUCT FROM SAID FIRST CHAMBER TO SAID CRANKCASE WHICH LEADS FROM THE LOWER PORTION OF SAID FIRST CHAMBER, ANOTHER CHAMBER OVERLYING SAID FIRST CHAMBER, VALVE MEANS BETWEEN SAID FIRST CHAMBER AND SAID OTHER CHAMBER, AND DUCT MEANS BETWEEN SAID OTHER CHAMBER AND THE ATMOSPHERE. 